The present invention relates to a hole-punching processor and an image forming apparatus, and in particular, to a hole-punching processor that forms a punched-hole for file binding on a sheet that is subjected to image forming and recording by an image forming apparatus such as, for example, a copying machine, a printer, a facsimile machine or a compound machine thereof and is ejected, and to an image forming apparatus equipped with the hole-punching processor.
In an image forming apparatus such as a copying machine, a printer, a facsimile machine or a compound machine thereof, there has been made an attempt to improve work efficiency by combining a hole-punching processor that forms a punched-hole for file binding with an image forming apparatus.
In processing of this punched-hole, it is important that punching is conducted at the same position constantly so that a position of a punched-hole may not be deviated on a sheet and the sheet may be trued up satisfactorily when the sheet is filed. However, a position of a punched-hole on each sheet is varied slightly by generation of sheet skewing or of a one-sided sheet in conveyance of each sheet, and thereby, positions of punched-holes turn out to be irregular even when edges of sheets having thereon punched-holes are trued up, thus, the sheets cannot be filed together, or edges of the sheets turn out to be irregular and awkward even if they can be filed, which has been a problem.
With the background stated above, there has been proposed a technology wherein a line sensor is arranged at the position corresponding to the width of a sheet that is led into a hole-punching device, and a position of a side edge of the sheet that is in parallel with the conveyance direction for the sheet is detected by the sensor, then, based on the result of the detection, the hole-punching device itself is moved in the direction of a width of the sheet so that a hole may be punched at the center of the sheet in its width direction (TOKKAIHEI No. 3-92299).
However, the line sensor needs to be provided to correspond to the sheet size, resulting naturally in a large size, and a problem of cost increase by an amount equivalent to the increase in size cannot be avoided.
On the other hand, there has been proposed a technology wherein a detecting means itself for detecting, corresponding to a width of a sheet to be led into a hole-punching device, a position of a side edge that is in parallel with the conveyance direction for the sheet is moved in the direction of a width of the sheet independently of the hole-punching device (TOKKAIHEI No. 10-279170).
The technology stated above makes it unnecessary to use a line sensor, and the aforesaid problem can be solved accordingly. However, it is impossible to avoid the problems that an apparatus grows greater and cost is increased, because a moving mechanism for the exclusive use for moving the detecting means and a driving means therefore are necessary.
There has further been proposed a technology wherein a hole-punching device is provided movably in the direction perpendicular to the conveyance direction for a sheet, and a side edge detection sensor (photo-sensor) for detecting a position of the side edge that is in parallel with the conveyance direction for the sheet to be led into the hole-punching device, and the side edge detection sensor is moved in the direction of the sheet width perpendicular to the conveyance direction for the sheet to detect a position of the side edge of the sheet, then, the hole-punching device is moved to the center of the sheet based on information of the detection results for hole-punching processing (TOKKAIHEI No. 10-279170).
In the hole-punching processor stated above, a sheet is ejected with its image surface facing downward because sheets are subjected to paginating in the order of outputting from the image forming apparatus main body and are stacked on a sheet ejection tray. However, when hole-punching processing is conducted on sheets conveyed in from the image forming apparatus main body, the hole-punching processing is usually conducted on the trailing edge portion in the conveyance direction. Therefore, it is necessary to form a conveyance path that conveys the leading edge of a sheet at the downstream side of the hole-punching device that punches a punched-hole. However, for avoiding a large-sized hole-punching processor, the aforesaid conveyance path is composed of a curved path in a shape of a curve so that a long conveyance path may be secured and an apparatus in a small size may be attained by narrowing the width as far as possible.
The hole-punching processor mentioned above makes it possible to correct skewing for sheets in various sizes fed in from the image forming apparatus main body, and then, to conduct hole-punching processing on the trailing edge of the sheet.
However, it is problematic in terms of conveyance reliability to convey a sheet like a thick sheet on which hole-punching processing cannot be conducted by using a conveyance path composed of a curved path. Further, when conducting hole-punching processing for the sheet that is short in size and is conveyed in from the image forming apparatus main body, or even when hole-punching processing is not conducted for a sheet, the sheet must be ejected through a longer distance, and the waiting time up to sheet ejection for the sheet is longer, which is a disadvantage to cause a decline in FCOT (First Copy Time) efficiency.
Further, for enhancing functions of an image forming apparatus more in general, there sometimes is an occasion to connect, in succession to a hole-punching processor, a finishing apparatus including a stapler that conducts staple processing for the sheet ejected from the hole-punching processor.
In the hole-punching processor, when a sheet is subjected to correction of skewing and to hole-punching processing, the preceding sheet that is being conveyed in the hole-punching processor is usually stopped temporarily each time, because driving of a conveyance motor is stopped temporarily to stop conveyance of the sheet temporarily. Therefore, when a leading edge of the sheet that is conveyed from an outlet of the hole-punching processor into the finishing apparatus in the subsequent step is in the state to be nipped by an entrance roller of the finishing apparatus, if the conveyance roller of the hole-punching processor is stopped temporarily, there is caused a phenomenon that the rotating entrance roller on the finishing apparatus side and the conveyance roller on the hole-punching processor side which is at a standstill pull the sheet each other, resulting in a problem that the sheet is soiled.